The present disclosure concerns devices and methods for controlling humidity at the surface of a supporting item of the mattress or cushion type and in the vicinity of the body of an individual resting thereon.
This humidity may originate from the body of the patient by the flow of a body liquid such as by sweating, or from an external source of spread liquid. Indeed, it is desirable to avoid maceration of liquid at soft tissues of the skin, whether this is an external liquid or sweat, because this humidification causes maceration which promotes formation of eschars and maintains foci of infection.
Methods and devices of this type are known, which consist of injecting air at the surface or towards the body of the individual, by applying said air loss mattresses or cushions (<<low-air-loss beds>>) consisting of compartments inflated with pressurized air. Thus, the body of the individual or the area between the body and the supporting item, i.e. the mattress at which humidity may be generated, is dried by the air flow oriented in this direction.
A first problem of this known device is that it cannot be applied independently of the supporting item, notably of the mattress and that interruption of the air injection inside the mattress results in it being made inoperative. Another drawback of this said air loss mattress system is that it may lead to excessive desiccation of the body and requires compensation of hydric losses by a program for hydrating the individual.
Dehumidification systems in the vicinity of a patient have been described which consist of a cover comprising an envelope inserted between the patient and the mattress, said envelope comprising an upper layer and a lower layer delimiting a chamber in which air is caused to flow. In these systems, it is sought to dehumidify the external surface of said upper layer on which said patient rests, at least in part with transfer of water vapor by molecular migration of water molecules through the upper layer of the envelope pervious to water vapor.
In U.S. Pat. No. 5,882,349, the lower layer of the envelope is impervious to air and to water vapor, and if necessary the air is injected into only a portion of the internal volume of said envelope through a plurality of injection ports, and is discharged by a plurality of perforations which may be positioned on the sides of the upper layer. This dehumidification system is comparatively not very performing with an announced dehumidification of only 400 ml/24 h.
In U.S. Pat. No. 5,926,884, a mattress coverlet of this type is described, wherein air is exclusively discharged through perforations in the upper layer over the whole surface and notably at the area covered by the patient, and the lower layer is pervious to water vapor. The thereby formed envelope between the lower layer and the upper layer, both pervious to water vapor, is completed with an additional underlying layer absorbing and dispersing water vapor which risks building up between the thereby formed dehumidification device and the mattress.
In these dehumidification devices by transfer of water vapor, partial discharge of air on at least the side of the patient resting on the device has risks of contaminating the envelope by penetration of liquid or another contaminant coming from the external surface of the upper layer on which the patient rests. On the other hand, and above all, the yields in terms of dehumidification, are either relatively small or they are accompanied by dehydration of the patient resulting from the excessive air flow sent in proximity to the patient.